/**
 * 方法四： 使用__proto__原型继承法
 */
 var Rectangle = {
    name: "Rectangle",
    
    getArea: function getArea() {
        return this.width * this.height;
    },
    
    getPerimeter: function getPerimeter() {
        return 2 * (this.width + this.heigth);
    }
    
    toString: function toString() {
        return this.name + " a=" + this.getArea() + " p=" + this.getPerimeter();
    }
 };
 
 // Make Square inherit from Rectangle by prototype
 /**********************************
 var Square = Object.create(Rectangle);
 Square.name = "Square";
 Square.getArea = function getArea() {
    return this.width * this.width;
 };
 Square.getPerimeter = function getPerimeter() {
    return this.width * 4;
 }
 ************************************/
 var Square = {
    __proto__: Rectangle,
    name: "Square",
    getArea: function getArea() {
      return this.width * this.width;
    },
    getPerimeter: function getPerimeter() {
      return this.width * 4;
    }
 var rect = Object.create(Rectangle);
 rect.width = 6;
 rect.height = 4;
 var square = Object.create(Square);
 square.width = 5;
 console.log(rect.toString());
 console.log(square.toString());